The distribution of liquids by formation of a fine spray, or atomization, is well known. One method for such distribution is to atomize a liquid by means of the acoustic vibration generated by an ultrasonic piezoelectric vibrator. An example of such a method is shown in Carter, U.S. Pat. No. 4,702,418, which discloses an aerosol dispenser including a nozzle chamber for holding fluid to be dispensed, and a diaphragm forming at least a portion of the chamber. An aerosol dispensing nozzle is disposed therein, with a restrictive passage for introducing liquid from the reservoir to the nozzle. A pulse generator in combination with a low voltage power source is used to drive a piezoelectric bender, which drives fluid from the reservoir through the nozzle to create an aerosol spray.
Another atomizer spraying device is shown by Humberstone et al, in U.S. Pat. No. 5,518,179, which teaches a liquid droplet production apparatus comprising a membrane which is vibrated by an actuator which has a composite thin-walled structure, and is arranged to operate in a bending mode. Liquid is supplied directly to a surface of the membrane and sprayed therefrom in fine droplets upon vibration of the membrane.
U.S. Pat. Nos. 5,297,734 and 5,657,926, of Toda, teach ultrasonic atomizing devices comprising piezoelectric vibrators with a vibrating plate connected thereto. In U.S. Pat. No. 5,297,734, the vibrating plate is described as having a large number of minute holes therein for passage of the liquid, and as being in physical contact with a liquid keeper such as a sponge.
In U.S. Pat. No. 4,301,093, Eck teaches the use of a wick of elastically resilient material which presses against the vibrating atomizer element, and covibrates with a more or less damped vibration amplitude. A wick tube surrounds the wick almost to the point of contact with the vibrating element.
Ivri et al, in U.S. Pat. No. 5,586,550, teach apparatus for the delivery of therapeutic liquids, including a vibratable non-planar member having tapered apertures, to which liquid is delivered by squeezing a liquid reservoir to deposit it directly on the surface, such that all of the liquid adheres to the vibratable member by surface tension. A piezoelectric element is bonded to a vibratory cantilever beam to provide oscillation to the carrier plate in contact with the non-planar member so as to nebulize the liquid in contact therewith.
Japanese Patent Publication 06320083A discloses an ultrasonic atomizer wherein a strong liquid storing material (e.g. a sponge) delivers liquid to a perforated diaphragm which is oscillated in response to piezoelectric vibration. The contact pressure of the liquid storing material against the diaphragm is kept constant by a spring tensioning device.
While a number of additional patents disclose means for the dispersion of liquids by ultrasonic atomization, or for timed intervals of dispersion, they have achieved only moderate success. See, for example, U.S. Pat. Nos. 3,543,122, 3,615,041, 4,479,609, 4,533,082, and 4,790,479. The disclosures of these patents, and of all other publications referred to herein, are incorporated by reference as if fully set forth herein.
However, such atomizers and/or dispensers fail to provide a system by which liquid to be dispersed is supplied to the vibratory mechanism/surface without resulting in damping of the piezoelectric vibrational frequency. Moreover, the prior art has failed to provide an easily portable, battery operated, continuous-action dispenser employing an orifice plate in mechanical connection with a piezoelectric element, capable of long periods of use with little or no variation in the delivery rate. Thus, a need exists for improved atomizers or dispensers for use in distribution of active fluids such as fragrances and insecticides, having improved means for supply of the fluid to be dispensed to the vibrating orifice surface.